1. Field of the Invention
The present invention relates to a fuel cell formed by stacking an electrolyte electrode assembly and a metal separator in a stacking direction. The electrolyte electrode assembly includes a pair of electrodes and an electrolyte interposed between the electrodes. A fluid passage extends through the fuel cell in a stacking direction for supplying a fluid comprising at least one of a fuel gas, an oxygen-containing gas, and a coolant in the stacking direction.
2. Description of the Related Art
For example, a polymer electrolyte fuel cell employs a power generation cell formed by sandwiching a membrane electrode assembly (MEA) between separators. The membrane electrode assembly includes an anode, a cathode, and an electrolyte membrane interposed between the anode and the cathode. In use, normally, a predetermined number of power generation cells are stacked together to form a fuel cell stack.
In the fuel cell, a fuel gas flow field (fluid flow field) for supplying a fuel gas (fluid) and an oxygen-containing gas flow field (fluid flow field) for supplying an oxygen-containing gas (fluid) are formed in surfaces of separators facing a cathode and an anode, respectively. Further, a fuel gas supply passage and a fuel gas discharge passage as fluid passages connected to a fuel gas flow field and an oxygen-containing gas supply passage and an oxygen-containing gas discharge passage as fluid passages connected an oxygen-containing gas flow field extend through marginal portions of the separators in the stacking direction.
Further, a coolant flow field (fluid flow field) for cooling the membrane electrode assembly is formed between the separators. A coolant supply passage and a coolant discharge passage as (fluid passages) connected to the coolant flow field extend through the separators in the stacking direction.
In the structure, the fluid flow field and the fluid passage are connected by connection channels such as parallel grooves for supplying the fluid smoothly and uniformly. However, at the time of tightening the separator and the electrolyte electrode assembly, and a seal member between the separator and the electrolyte electrode assembly, the seal member enters the connection channels undesirably. Thus, the desired sealing performance cannot be maintained, and the reactant gas does not flow smoothly.
In this regard, in a polymer electrolyte fuel cell stack disclosed in Japanese Laid-Open Patent Publication No. 2001-266911, as shown in FIG. 14, a reactant gas flow field comprising grooves in a serpentine pattern, e.g., an oxygen-containing gas flow field 2 is formed in a surface of a separator 1. The oxygen-containing gas flow field 2 is connected to an oxygen-containing gas supply passage 3 and an oxygen-containing gas discharge passage 4. The oxygen-containing gas supply passage 3 and the oxygen-containing gas discharge passage 4 extend through marginal portions of the separator in a stacking direction. Packings 5 are provided in the separator 1. The packings 5 seal the passages 3, 4 from other passages, while allowing the passages 3, 4 to be connected to the oxygen-containing gas flow field 2.
SUS plates (stainless steel) 7 as seal members are provided in connection channels 6a, 6b connecting the passage 3, 4 and the oxygen-containing gas flow field 2. Each of the SUS plates 7 has a rectangular shape having two ears 7a, 7b at two positions. The ears 7a, 7b are fitted to steps 8 formed in the separator 1. Therefore, in the conventional technique, the SUS plate 7 covering the connection channels 6a, 6b prevents the polymer membrane (not shown) and the packing 5 from being stuck in the grooves of the oxygen-containing gas flow field 2, making it possible to ensure sealability and prevent increase in the pressure loss of the reactant gas.
However, in the conventional technique, the SUS plates 7 are attached to connection channels 6a, 6b of the separator 1, respectively. Thus, operation of attaching the SUS plates 7 is laborious. In particular, in the case where several tens to several hundreds of fuel cells are stacked together, the process of attaching the SUS plates 7 is considerably complicated, and time consuming. Thus, the cost of fabricating the fuel cells is significantly high.